A major problem in the poultry industry is the high incidence of infectious diseases which reduce hatchability, increase the cull rate, reduce livability during growout and increase the condemations at the processing plant. It has thus become standard practice in commercial hatchery operations to immunize the birds against such diseases. The most widely used method of accomplishing this immunization is to manually inoculate (by injection of a suitable antibiotic or vaccine) each individual bird after it has been hatched. A skilled operator using automatic equipment can manually inject approximately only 2,000 young birds per hour. The operation is thus relatively expensive.
Another method of inoculation which has become quite popular in turkey hatcheries is egg dipping, whereby a temperature differential or vacuum is used to force the antibiotic solution through the shell of the embryonated egg. This method has the advantage of lower labor cost than manual inoculation; however, because of varying shell porosity and thickness, the amount of solution absorbed by the egg varies dramatically.
A test of 6,174 dipped eggs revealed that 18% of the eggs took in essentially no solution at all and an additional 36% took in too little to be effective. From this test, it was concluded that dipping cannot stop the perpetuation of disease and even encourages the development of organisms resistant to these few antibiotics which are now effective.
Because of the high solution cost and uncertainties associated with dipping, few chick hatcheries dip eggs and almost all hatcheries that do dip eggs (primarily turkey hatcheries) also manually inoculate the day-old birds.
Another method of inoculation involves the use of a hypodermic needle to inject a known quantity of injection liquid into the egg. In the past, eggs have been injected by hand. The operator would use a drill to make a small hole in the shell. A hypodermic needle would be inserted through the hole and a precise amount of solution injected. The hole would then be sealed with cement. It is estimated that eight operators can manually inject 25,000 eggs per day by this method.
An automatic egg injection machine and method are disclosed in U.S. Pat. No. 4,040,388. With this system a plurality of eggs resting in a tray having an apertured bottom are injected from below by a plurality of vertically disposed needle assemblies carried by a vertically movable injection device. Upward movement of the device engages the needle assemblies with the lower ends of the eggs whereupon heating elements in the needle assemblies sterilize portions of the shells. Subsequently each needle is moved upwardly out of its respective needle assembly so as to puncture the shells at the sterilized areas. A separate drive means is provided for each needle. Subsequently injection liquid is injected through the needles, the needles are withdrawn and the heating elements are activated to coagulate albumin at the location of the injection holes so as to seal the holes.